Thread Former Having Molding

ABSTRACT

The thread former is used for the non-cutting shaping of threads and has a main body ( 1′ ) on which the moldings ( 6 ) are provided, distributed over the circumference. Said moldings are provided with thread-forming teeth ( 13, 14 ). Profile grinding tools are used to produce the thread-forming teeth ( 13, 14 ), both in the main body ( 1′ ) as well as in the moldings ( 6 ). In order for the thread former to be produced easily and cost-effectively, the moldings ( 6 ) protrude radially beyond the main body ( 1′ ) so far that the profile tool only engages with the molding when producing the thread-forming teeth ( 13, 14 ). Consequently, the profiling tool only has to machine one type of material. The thread former is used for the non-cutting shaping of threads, particularly of internal threads.

The invention concerns a thread former according to the preamble ofclaim 1.

Thread formers serve for non-cutting shaping of threads. The free end ofthe main body constitutes a working part that, distributed about thecircumference, has moldings. The working part has a polygonalcross-section. In the area of the cross-sectional corners, the moldingsin the form of cylindrical bars are provided that consist of hard andwear-resistant material. The moldings are soldered into grooves of themain body. In particular the common profile grinding for producing thethread-forming teeth in the main body and in the inserted moldingscauses difficulties because the grinding wheels that are used for thispurpose clog quickly.

It is the object of the invention to develop the thread former of theaforementioned kind such that it can be produced in a simple andcost-effective way.

This object is solved for the thread former ofthe aforementioned kind inaccordance with the invention with the characterizing features of claim1.

In the thread former according to the invention, the moldings projectradially past the main body to such an extent that with the profilingtool, preferably a grinding wheel, only the moldings for generating thethread-forming teeth are cut while the profiling tool no longer comesinto contact with the main body. The profiling tool must only cut onekind of material so that the manufacturing process becomes simpler andfaster. The profiling tool can therefore be selected optimally withrespect to its profiling task.

The moldings are advantageously fastened in receiving grooves of themain body. In the receiving grooves, the moldings can be fastenedreliably, for example, by soldering or by an adhesive. The moldingsadvantageously can be formed to be symmetrical to their longitudinalcenter plane. However, it is also possible that the moldings are formedto be asymmetrical relative to their longitudinal center plane.

The moldings can be arranged axis-parallel, i.e., the longitudinal axisof the thread former is positioned in the longitudinal center plane ofthe moldings. The bottom of the receiving grooves extends in this caseparallel to the axial plane of the thread former.

Depending on the type of use of the thread former, it is also possiblethat the moldings are positioned at an angle to a correlated axialplane. In this case, the bottom of the receiving grooves extends fromthe free end of thread former at a slant in the direction toward theexterior side of the thread former.

The moldings, in a side view, can be positioned at an angle relative tothe longitudinal axis of the thread former wherein the moldings mayextends straight as well as in a spiral shape.

In one embodiment, the moldings are advantageously arranged uniformlydistributed about the circumference of the main body.

In case of particularly long thread formers or in case of thread formersthat operate at very high cutting speeds, it is advantageous when themoldings are arranged in non-uniform distribution about thecircumference of the main body. Such non-uniform distribution leads tosmoother running of the thread former.

The moldings can be arranged symmetrically to the axial plane of themain body in such a way that their longitudinal plane is located in thecorresponding axial plane of the moldings.

It is however also possible that the moldings are arranged such thattheir longitudinal center plane is positioned at an acute angle relativeto the correlated axial plane of the main body that extends through themoldings.

The area between neighboring moldings can be used for supplying coolinglubricant to the processing site. However, it may also be advantageousto provide the thread former with an inner cooling medium supply. Inthis way, the cooling medium can be applied in a targeted fashion to theprocessing site of the thread former.

Further features of the invention result from further claims, thedescription, and drawings.

The invention will be explained in more detail with the aid of someembodiments illustrated in the drawings. It is shown in:

FIG. 1 in perspective illustration a first embodiment of a thread formeraccording to the invention;

FIG. 2 the thread former according to FIG. 1 in a side view;

FIG. 3 in a detail view an end face of the thread former according toFIG. 1.

FIG. 4 to FIG. 6 in an end view, respectively, further embodiments ofthread formers according to the invention;

FIG. 7 in perspective illustration a further embodiment of a threadformer according to the invention whose moldings are illustrated onlyschematically;

FIG. 8 in a side view the thread former according to FIG. 7;

FIG. 9 in a detail view an end face of the thread former according toFIG. 7;

FIG. 10 to FIG. 12 in illustrations according to FIGS. 7 to 9 a furtherembodiment of a thread former according to the invention;

FIG. 13 and FIG. 14 in a side view, respectively, the thread formeraccording to the invention with inner cooling action;

FIG. 15 in an end view a further embodiment of a thread former accordingto the invention

The thread formers disclosed in the following serve for non-cuttingshaping of threads. In particular, with the thread formers internalthreads are formed. The thread former according to FIGS. 1 to 3 has amain body 1′ with a preferably cylindrical clamping shaft 1 with whichit is received in a tool receptacle. The clamping shaft 1 is provided atone end with a profiled section 2 with which positive fit of the threadformer in the tool receptacle in rotational direction is achieved.

The clamping shaft 1 passes with a short conical intermediate section 3into a preferably cylindrical end section 4. It has a smallercross-sectional surface area than the clamping shaft 1 in the areabetween the profiled section 2 and the intermediate section 3. The endsection 4 is adjoined by a head section 5 to which moldings 6 areattached in a way to be described in the following. In deviation fromthe illustrated embodiment, the main body 1′ can have across its lengthany other suitable cross-sectional configuration.

The clamping shaft 1 with the profiled section 2, the intermediatesection 3, the end section 4, and the head section 5 is of a monolithicconfiguration and is comprised of a tough material, for example, ahigh-speed steel. The head section 5 has a conically tapering end.

The head section 5 is provided with receiving grooves 7 for receivingthe moldings 6 that extend axially away from the end face 8 of the headsection 5. The receiving grooves 7 extend, for example, approximatelyabout half the axial length of the head section 5. Depending on thedesign of the thread former, the receiving grooves 7 and thus also themoldings 6 disposed therein can also have different lengths. Thereceiving grooves 7 end at a minimal spacing from the end section 4 bytapering into the exterior side of the head section 5. The receivinggrooves 7 can be introduced in a very simple and inexpensive way intothe head section 5 by means of a grinding wheel. As can be seen in FIG.3, the receiving grooves 7 have a planar bottom 9 that connects twoparallel extending planar lateral surfaces 10, 11 with each other. Thebottoms 9 of the receiving grooves 7 are positioned tangentially to animaginary circle about the longitudinal axis 12 of the thread former.The moldings 6 are attached to the receiving grooves 7, for example, bysoldering, by an adhesive, by welding or other conventional joiningmethods. An additional form-fitting action of the moldings 7 in thereceiving grooves 7 is advantageous but not necessarily required.

As is illustrated in FIG. 2, the moldings 6 project radially past thehead section 5. This radial projection of the moldings 7 is so largethat when forming the thread exclusively the moldings 6, but not themain body 1′, will contact the respective workpiece. The moldings 6 canbe made of hard metal, cermet, CBN, diamond or other cutting materialsof great hardness.

The moldings 6 have at their exterior side thread-forming teeth 13, 14(FIG. 2) positioned at a spacing behind each other which extend acrossthe width of the moldings 6. The thread-forming teeth 13, 14 have acrosstheir length a constant pitch in order to generate the desired thread inthe bore wall. The thread-forming teeth 13 that are neighboring theplanar end face 8 have a smaller outer diameter than the subsequentlyarranged thread-forming teeth and serve for a stepwise forming of thethread during thread manufacture. In this way, it is achieved that thethread depth is not generated in a single pass but that first the threadis produced only over a portion of its profile depth in the bore walland only the following thread-forming teeth 13 will complete the threadto the full profile depth. Also, depending on the configuration of thethread former, only one or several thread-forming teeth 13 may beprovided in the initial thread-forming area of the thread former. In theembodiment, in the initial thread-forming area of each molding 6 thereare three thread-forming teeth 13. The following thread-forming teeth 14serve for guiding the thread former during the process of threadforming.

The moldings 6 have advantageously a rectangular cross-section. Thelonger side 15 of the cross-section (FIG. 3) of the molding 6 is facingthe bottom 9 of the receiving groove 7, preferably is connected to it.The moldings 6 of course can also have different cross-sectional shapes,for example, round or polygonal cross-section. As shown in FIG. 3, thethread-forming teeth 13, 14 are curved in circumferential direction ofthe thread former such that, in plan view according to FIG. 3, they haveat half the length the greatest spacing from the longitudinal axis 12 ofthe thread former. The thread-forming teeth 13, 14 extend about arelatively great length in the circumferential direction of the headsection 5. For example, the thread-forming teeth 13, 14 extend about anangle range between approximately 30 degrees and 60 degrees, preferablyapproximately about 45 degrees. In the embodiment according to FIGS. 1to 3, the moldings 6 are embodied and arranged symmetrical to therespective axial plane 16 of the thread former.

The moldings 6 have about the circumference of the head section 5 anangular spacing of 90 degrees relative to each other. Betweenneighboring moldings 6 intermediate spaces 17 are formed by means ofwhich during the thread forming process a cooling lubricant can besupplied to the processing site.

Since the thread-forming teeth 13, 14 are provided exclusively on themoldings 6, during manufacture of the thread-forming teeth 13, 14 orwhen they are re-ground the grinding wheel must cut only one type ofmaterial so that the manufacturing process becomes simpler and faster.

The bottom 9 of the receiving groove 7 may extend parallel to an axialplane 16 of the thread former. The moldings 6 are formed such that theircross-sectional thickness, beginning at the end face 8 of the threadformer, increases in axial direction continuously. The moldings 6 arearranged axis-parallel on the head section 5. The moldings 6 may also beattached conically in relation to the longitudinal axis 12 of the headsection 5. In this case, the moldings 6 extend from the end face 8 ofthe head section 5 at a slant outwardly.

With the aid of FIGS. 4 to 6 it will be explained in an exemplaryfashion that the moldings 6 can also be arranged non-uniformity aboutthe circumference of the head section 5 as well as angled relative tothe corresponding axial planes.

FIG. 4 shows the situation that oppositely positioned moldings 6 a, 6 cand 6 b, 6 d are displaced at a minimal angle relative to each other.All of the moldings 6 a to 6 d are symmetrical to their correlated axialplane 16 or their longitudinal center plane 24. The axial planes 16 ofthe oppositely positioned moldings 6 a, 6 c and 6 b, 6 d are positionedat an angle that deviates slightly from 180 degrees relative to eachother, respectively. The arrangement of the moldings 6 a to 6 d alongthe circumference of the head section 5 is selected such that themoldings 6 a and 6 b as well as 6 d and 6 c have a smaller spacingrelative to each other than the moldings 6 a and 6 d or 6 d and 6 d.With this non-uniform distribution of the moldings about thecircumference of the head section 5 a smoother running of the threadformer during thread forming is achieved. In particular, thisnon-uniform distribution of the moldings 6 a to 6 d is advantageous forespecially long thread forms. Also, in case of thread formers thatoperate at very high cutting speeds the moldings 6 a to 6 d that arenon-uniformly distributed about the circumference of the head section 5calm the running of the threat former.

The thread former according to FIG. 4 can also be designed such that,for example, the moldings 6 a, 6 c are positioned diagonally oppositeeach other while the moldings 6 b, 6 d are displaced in circumferentialdirection relative to each other. In this way, a non-uniformdistribution of the moldings is achieved also.

FIG. 5 shows the possibility to distribute the moldings 6 uniformlyabout the circumference of the head section 5. In contrast to thepreceding embodiments the moldings 6 are however fastened to the threadformer in such a way that the longitudinal axes 24 of the moldings 6 arepositioned at an angle relative to the axial planes 16 that extend atthe radial external side of the moldings through their center 18.Moreover, the moldings 6 are not arranged to be axis-parallel on thehead section 5 but extend in longitudinal direction of the head section5 at a slant. Oppositely positioned moldings are arranged such that theaforementioned center 18 is positioned in the outer radial area of themoldings on a common axial plane 16, respectively. The two axial planes16 of the moldings 6 that are formed in this way are positioned at aright angle to each other. The moldings 6 are of identical design andarranged on the head section 5 slantedly in the same direction. In otherrespects, the moldings 6 are of the same configuration as in thepreceding embodiments.

FIG. 6 shows in an exemplary fashion that the moldings 6 in deviationfrom the preceding embodiments may also have an asymmetricalcross-section. The moldings 6 themselves are positioned diametricallyopposed to each other on the head section 5 in the way described.Moreover, the moldings 6 are uniformly distributed about thecircumference of the head section 5. As a result of the asymmetriccross-sectional configuration, the part 18 of each molding 6 that ispositioned farthest outwardly in radial direction is no longerpositioned at half the width of the molding. The axial planes 16 of thethread former that extend through this outer point 18 of the moldingsare positioned at an angle deviating from 90 degrees relative to thebottom 9 of the receiving groove 7 or to the cross-sectional side 15 ofthe moldings 6. The moldings 6 themselves are positioned axis-paralleland, as in the embodiment according to FIGS. 1 to 3, can be positionedwith their cross-sectional side 15 parallel to the respective axialplane 16 but may also be positioned an acute angle relative thereto.

In the described embodiments the thread-forming teeth 13, 14 each havepressing edges 19 that, in the embodiments according to FIGS. 1 to 5,are ground centrally relative to the molding. In this way, the part 18that is positioned farthest outwardly in radial direction of eachmolding 6; 6 a to 6 d is positioned of half the length of these pressingedges 19. In the embodiment according to FIG. 6 the pressing edges 19are ground off-center relative to the molding 6 so that the part 18 ofthe pressing edges 19 that in radial direction projects farthestoutwardly no longer is positioned at half the length of the pressingedges.

FIGS. 7 to 9 show a thread former where the moldings 6 are arranged withthe same pitch, respectively, along the circumference of the headsection 5 of the thread former. The receiving grooves 7 extend from theplanar end face 8 of the thread former into the end section 4. Themoldings 6 are each of same configuration and, relative to theirlongitudinal center plane 24, of a symmetrical cross-section. Themoldings 6 have the thread-forming teeth 13, 14 with which the thread isproduced in the workpiece and with which the thread former is guided.Each molding 6 has a planar end face 20 that is positioned in the planarend face 8 of the head section 5. A slanted surface 21 adjoins the endface 20 at an obtuse angle. The moldings 6 can be arrangedaxis-parallel. In the embodiment, the moldings 6 have also a rectangularcross-section. With their cross-sectional side 15 the moldings 6 restsagainst the bottom 9 of the receiving grooves 7. The receiving grooves 7can be designed such that their bottom 9 extends parallel to an axialplane of the head section 5. However, it is also possible that thebottom 9 extends at an acute angle to the corresponding axial plane ofthe head section 5.

FIGS. 10 to 12 show a thread former in which the receiving grooves 7 forthe moldings 6 extends also into the end section 4. The moldings 6themselves extend in accordance with the preceding embodiment onlyacross a portion of the length of the head section 5. In contrast to thepreceding embodiment the receiving grooves 7 have only a minimal pitchso that accordingly also the moldings 6 have only a minimal pitch. Thepressing edges 19 of the moldings 6 are ground, as in the precedingembodiment, centrally relative to the molding 6. As illustrated in FIG.12, the moldings 6 are positioned at an angular spacing of 90 degreesrelative to each other. In other respects, the thread former is of thesame configuration as the embodiments according to FIGS. 1 to 4.

The thread formers can also be provided with an inner cooling mediumsupply in order to convey the cooling medium into the processing area.FIG. 13 shows in an exemplary fashion a central axial cooling bore 22that extends from the clamping end 2 into the head section 5. Coolingmedium bores 23 extend at a slant outwardly away from the cooling mediumbore 22 and open into the area between neighboring moldings 6 at thehead section 5. The cooling medium is thus directly transported duringthread-forming action through these cooling medium bores 22, 23 into theprocessing area of the thread former so that an optimal cooling actionis ensured.

In the exemplary illustrated embodiment according to FIG. 14 only thecentral cooling medium bore 22 is provided that opens at the end face 8of the thread former.

FIG. 15 shows in an exemplary fashion the possibility to configure themoldings also with a different cross-sectional shape. In the precedingembodiments the moldings 6 have an angled cross-section. In thisembodiment, the outer side 15 of the molding 6 facing the bottom 9 ofthe receiving grooves 7 is in cross-section of partcircular shape. Thebottom 9 of the receiving grooves 7 has also a matching cross-sectionalshape. The moldings 6 are positions with their curved outer side 15 inflat contact on the curved bottom 9 of the receiving grooves 7. The arearadially projecting past the head section 5 of the moldings 6 isprovided with the thread-forming teeth 13, 14 with the pressing edges19.

When the moldings 6 and the head section 5 of the thread former in apreferred way are connected by soldering or adhesive connectiondetachably with each other, a simple refurnishing of the thread formerby reusing the main body 1′ is ensured. It is only necessary to exchangethe moldings 6. The thread former with the moldings 6 can be providedwith wear protection layers or friction-reducing layers. In this way, along service life of the thread former is achieved.

In the described and illustrated embodiments the thread former has fourmoldings. Depending on the application and/or size, the thread formercan also have fewer than or more than four moldings.

1.-13. (canceled)
 14. A thread former comprising: a main body; moldingsdistributed about a circumference of the main body and provided withthread-forming teeth; wherein the moldings project radially so far pastthe main body that a profiling tool during manufacture of thethread-forming teeth engages only the moldings.
 15. The thread formeraccording to daim 14, wherein the main body has receiving grooves andthe moldings are fastened in the receiving grooves.
 16. The threadformer according to daim 14, wherein the moldings each have alongitudinal center plane and are embodied symmetrical relative to thelongitudinal center plane.
 17. The thread former according to daim 14,wherein the moldings each have a longitudinal center plane and areembodied asymmetrical relative to the longitudinal center plane.
 18. Thethread former according to claim 14, wherein the moldings are arrangedaxis-parallel to an axis of the main body.
 19. The thread formeraccording to claim 14, wherein the moldings are positioned at an anglerelative to an axial plane of the main body.
 20. The thread formeraccording to claim 14, wherein the moldings, viewed in a side view, arepositioned at an angle relative to a longitudinal axis of the main body.21. The thread former according to claim 14, wherein the moldings extendspirally about the main body.
 22. The thread former according to claim14, wherein the moldings are arranged uniformly distributed about thecircumference of the main body.
 23. The thread former according to claim14, wherein the moldings are arranged non-uniformly distributed aboutthe circumference of the main body.
 24. The thread former according toclaim 14, wherein the moldings are symmetrically arranged relative to anaxial plane of the main body.
 25. The thread former according to claim14, wherein the moldings are arranged such that a longitudinal centerplane of the moldings is positioned at an acute angle relative to anaxial plane of the main body.
 26. The thread former according to daim14, comprising an inner cooling medium supply.